It is known in the magnetic drill art to provide accessory support plates for a magnet base drill for mounting a drill on a convexly shaped support surface. An example of such prior art accessory support plates is disclosed in U.S. Pat. No. 4,047,827. A disadvantage of the support plates shown in U.S. Pat. No. 4,047,827 is that they do not have sufficient holding power for mounting a magnet base drill on vertically disposed pipes and the like. A further disadvantage of the last mentioned accessory support plates is that they will only fit certain magnet base drills which have been previously prepared for use with the same.
Further examples of support means for magnet base drills are illustrated in the U.S. Pat. No. 3,791,755, and a French patent No. 896,945 issued in May, 1944 and another French patent No. 1,260,819 issued in March, 1961. The last three mentioned patents are cited as prior art patents in U.S. Pat. No. 4,047,827.